<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>onchange 事件案例</title>
</head>

<head>
    <script>
        function myFunction() {
            var x = document.getElementById("fname");
            x.value = x.value.toUpperCase();
        }
    </script>
</head>

<body>

    输入你的名字: <input type="text" id="fname" onchange="myFunction()">
    <p>当你离开输入框后，函数将被触发，将小写字母转为大写字母。</p>

</body>

</html>